Internal angle of a regular polygon 

To remember the formula for the internal angle of a regular (each side is equal) polygon, you should always work out the first three polygons, i.e triangle, square and pentagon.

Therefore, the sum of all the internal angles 

`=((Number  of  sides -2)times180)/(Number  of  sides)`  

which is often shown as

`=((n-2)times180)/(n)`  

where n is the number of sides.